1. Field of the Invention
This invention relates to charging for services in a communication system such as a mobile telephony system.
2. Description of the Related Art
In a basic communication system a simple communication network is provided, which can link together two communication terminals so that the terminals can communicate with each other in a communication session or call. Conventionally, a designated entity in the network uses a stored tariff to determine a charge for a call based on the call's duration. Each terminal user has a charging account with the operator of the network. The charge for a call is then allocated to the charging account of the user of the terminal that originated the call. When a call is in progress the network may use the tariff to estimate the charge due in respect of the call so far. The network may periodically transmit that estimated charge to the terminal that originated the call, and the estimated charge may then be displayed by that terminal so that its user can see the ongoing cost of the call.
However, for third generation (3G) communication systems the systems of more than one operator may be used for carrying a call, and operators of all of those systems may be able to levy charges independently for the services they provide in supporting the call. A system of this sort applies the charges made by a number of operators for a single call to the correct account by generating charging data records (CDRs) that include a global charging identifier (ICID) that relates to a call. The global charging identifier may be generated by the first network entity to begin charging for a call, or by the first entity to generate a CDR. It is therefore necessary for different network entities to support ICID generation.
It is therefore an aim of embodiments of the present invention to overcome the need for different network entities to support ICID generation.